The present invention relates to lighting fixtures and luminaires, and more particularly to an improved optical assembly including a combination of a reflector/refractor device and an optical control overlay device called a shroud.
Various arrangements are known for reflectors when used as lighting fixtures and luminaires. Some known reflectors are manufactured in metals such as aluminum and steel, or of a glass or plastic. These materials are then painted, plated, or chemically brightened to function as reflectors. Vacuum metallizing, vapor or chemical deposition can be used to place a thin metal layer onto the surface of the metal, plastic or glass to act as reflector. When a very thin transparent metal layer is vacuum metalized or vapor deposited on a transparent plastic or glass contour, the coverage is often random and may produce a non-uniform appearance which causes the performance to be unpredictable. There are also prismatic internal reflection glass and plastic reflectors which use the index of refraction to control the reflectance of light and redirect it into a distribution of light. Some glass reflectors are known to use a metal cover spun around the exterior to eliminate uplight, radiated by the large rounded portion of their prism peaks and roots, and the cover is used as a means of glare control and to maintain a clean exterior internal reflection surface. However, this creates a very dark reflector exterior and a very bright aperture brightness, and when installed in a room this reflector produces very reduced uplight with no means of adjusting the glass reflectors"" reflected surface brightness to any other ambient lighting concerns or conditions.
Improvements over prior art arrangements have been provided by prismatic reflector/refractor, such as disclosed in the following United States patents.
U.S. Pat. No. 4,839,781 issued to Josh T. Barnes and Ronald J. Sitzema Jun. 13, 1989 and assigned to the present assignee, discloses a reflector/refractor device for use with a variety of lighting fixtures and light sources. The reflector/refractor device includes a body having a predetermined profile and defining a cavity with the body having an inside surface and an outside surface. An illuminating source for emitting light is disposed within the cavity substantially along a central vertical axis of the body. The body includes a series of sectional zones for reflecting and refracting light. The exterior surface of the device includes a plurality of substantially vertical prisms consisting of reflective elements, refractive elements and elements that may be either reflective or refractive depending on light center location. These reflective or refractive elements act in combination to selectively vary light distribution characteristics of vertical and lateral angles, and intensities, by vertical displacement of the illuminating lamp source.
U.S. Pat. No. 5,444,606 issued to Josh T. Barnes and Paul C. Belding Aug. 22, 1995 and assigned to the present assignee, discloses a combination of a prismatic reflector and a prismatic lens is provided for use with lighting fixtures. A reflector body has a substantially parabolic contour defining an interior cavity. The reflector body includes a plurality of prisms for receiving, transmitting and reflecting light. A lens body has a first mating surface engaging the reflector body, an opposed inverted conical surface, and a sloping sidewall extending between the mating surface and the opposed inverted conical surface. The mating surface of the lens body has a larger diameter than the opposed inverted conical surface. The opposed inverted conical surface includes a plurality of prisms for receiving and for redirecting light.
A need exists for an effective mechanism for controlling the uplight and surface luminance in the 60-90 degree glare zone, from prismatic reflectors. One known arrangement encloses the exterior of a prismatic glass reflector in aluminum as a means of controlling the uplight. This arrangement creates a dark black surface in the 60-90 degree glare zone in contrast to a bright opening at the bottom of the reflector. The use of paint on the exterior surface of prismatic reflectors causes the refraction index on the material to change by eliminating the air/plastic interface and this allows the paint to absorb a large portion of the illumination that strikes the painted surface resulting in a significant loss of efficiency of the optical assembly performance.
Another known arrangement simply encloses the reflector with a smooth, clear or white, cover. This arrangement protects the prism reflecting surfaces from deposits that could interfere with their total internal reflecting properties. A simple smooth cover may work as a dust cover; however, this arrangement fails to provide any improvement in the control or contrast of the uplight component or to the surface luminance in the 60-90 degree glare zone, down-light component of the prismatic reflector. Molding a prismatic glass or plastic reflector in a specific color causes large efficiency losses in the performance, as the molded in color will absorb all other colors and only reflect the color that the reflector is molded in. This essentially makes the reflector a monochromatic reflected light source while the lamp may produce white light.
It is desirable to provide an optical assembly enabling improved optical control of an uplight illumination component. It is desirable also to provide an optical assembly enabling improved optical control of a downward illumination component enabling the reduction of glare between the 60xc2x0 and 90xc2x0 vertical angles of viewing. It is desireable to selectively produce colored uplight from the optical assembly in certain lighting installations, without creating large losses in efficiency, or creating a monochromatic reflected light from the molded-in pigmented reflector prisms.
A principal object of the present invention is to provide an optical assembly enabling improved optical control of an uplight illumination component and a downward illumination component enabling the reduction of glare between the 60xc2x0 and 90xc2x0 vertical angles of viewing. Other important objects of the present invention are to provide such optical assembly substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, an optical assembly enables improved optical control of an uplight illumination component and a downward illumination component. The optical assembly includes a reflector/refractor device and a shroud carried by the reflector/refractor device. The reflector/refractor has a predefined shape and has a plurality of reflector/refractor prisms on an exterior body surface for reflecting and refracting light. The shroud has a plurality of prisms disposed proximate to the reflector/refractor prisms for providing optical control of incident light from the reflector/refractor body.
In accordance with features of the invention, the shroud is formed substantially corresponding to the predefined shape of the reflector/refractor, surrounding and spaced from the reflector/refractor exterior body surface. The shroud is formed, for example, by vacuum forming or by injection molding technique. The shroud provides optical control of incident light from the reflector/refractor body, generally refracting incident light from the reflector/refractor body. The shroud prisms are generally aligned with the reflector/refractor prisms. The reflector/refractor prisms and the shroud prisms are substantially vertical prisms. The shroud is formed of a light transmitting material, such as a transparent or translucent polymeric material. The shroud optionally is formed by blending transparent materials having different refractive indices, and optionally by adding a pigment to an otherwise transparent material. The shroud optionally includes such pigmentation to provide a selected color for the optical assembly. The shroud optionally is metalized or pigmented to block the uplight component or to provide a portion of the transmitted illumination to certain uplight areas, or reflect and block the illumination.